Hulk's got back! How 'Thor: Ragnarok' gave the ginormous Avenger an incredible new butt

Warning: This post contains spoilers for one of Thor: Ragnarok’s best jokes.

Turns out the destruction of Asgard is only the second most memorable image in Thor: Ragnarok. In terms of size and scale, nothing dwarfs the incredible sight that is the Hulk’s bare butt. For the first time ever in a live action movie, Marvel’s resident green giant (played by Mark Ruffalo in motion-capture form) reveals his mammoth backside not only to his “friend from work,” the Mighty Thor (Chris Hemsworth), but also millions of moviegoers around the world.

The task of capturing Hulk’s butt in all its emerald glory fell to Ragnarok visual effects supervisor Jake Morrison, who accepted the challenge without complaint. “It was a really extraordinary thing to be asked to do,” Morrison semi-jokingly tells Yahoo Entertainment. “We weren’t sure how to heavily to lean in on that joke, but then we realized that we’re probably never going to do this again, so we had to embrace the moment.”

Hulk’s rear-end reveal occurs midway through Ragnarok, after he’s bested Thor in Sakaar’s gladiatorial arena. (Although that victory really should come with an asterisk because it’s owed primarily to some last-minute intervention by Jeff Goldblum‘s cheating Grandmaster.) Enjoying a dip in the hot tub back at his deluxe apartment in the Sakaaran sky, the Goliath emerges from the water and strolls casually over to the window, neglecting to wrap a towel around his waist as he moons his fellow Avenger.

Morrison cheekily refers to this scene as the Hulk’s “Michael Douglas from Fatal Attraction” moment. “I had to alter the [digital] Hulk model pretty significantly to accommodate it,” he reveals. “We had to venture where no Hulk modeler had gone before! Our only direction was that it had to look funny. Now, you can interpret that any way you like. Our interpretation was to not make it hairy, but rather a cartoonishly perfect bubble butt.”

But you’ll only be able to enjoy the fruits of their labors if you see the film on standard screens and bypass Imax theaters. “There is no Hulk butt in the Imax version,” Morrison says. “For a lot of the sequences, there’s a little bit more on the top and bottom [of the frame] in Imax. We didn’t do that with that shot!”

Even if Hulk’s bulbous butt had remained covered, Morrison says, his team would still have had to make significant alterations to the version of the character that has appeared in previous Marvel movies. That’s because this Hulk doesn’t only growl and smash: He also tells jokes. (And yes, that really is Ruffalo cracking wise, not O.G. Hulk Lou Ferrigno.) “There’s a lot more going on facially, and Mark performed all the motion capture stuff with head-mounted cameras,” Morrison explains. “So we said, ‘How can we make it look more like Mark?’ There’s also a story justification for that, because Bruce Banner has been trapped inside Hulk for two years, so some of him has bled through.”

In order to build a more perfect union of man and monster, Morrison’s F/X wizards went back to “first principals” in partnership with Lucasfilm’s Industrial Light & Magic effects shop, looking at early 3D sculptures and concept art drawn by Marvel’s visual development head Ryan Meinerding for the Hulk as he appeared in the first Avengers film, as well as Age of Ultron. “They made him more of a brute and less of a person [in those films],” Morrison says. “But Ryan’s initial sketches showed some really great character stuff for the face. The head was more of a cube, and has that chiseled jaw that you get with every leading man in the comic books. So we went to ILM and said, ‘We need to be shooting more towards that,’ and they started the whole thing from scratch.”

During production, Meinerding served as the intermediary between ILM and Morrison’s team, making touch-ups to individual frames that would be incorporated into the finished version of the Hulk as he appears in Ragnarok. “We probably went through hundreds of iterations before we landed on something we liked,” he says. “In the film, I can really see Mark in the Hulk. The facial structure is there, the performance is there. This is the dude that’s been nominated for an Oscar three times!” Yes, but the more important question remains, is Ruffalo happy with the way his butt looks in Hulk form? “He loves it,” Morrison confirms with a good-natured chuckle. “It’s very flattering in the best possible case.”